The nail-biting opening sequence in "The Expendables 3" is right up there with the best of the Bondian prologues.

A train covered with armed guards, hurtling down the track, is delivering a dangerous prisoner. A helicopter, also carrying plenty of men with guns, is on its way to relieve the train of that prisoner. Let the bullets fly, let the stuntmen tumble. But you know that our heroes, the Expendables, or at least what's left of them from the first two entries in this adrenaline-charged series, are going to get their man.

He's called Doc (Wesley Snipes), and he turns out to be one of the original Expendables, a member before that first story was ever told. He's been in the hoosegow for eight years, and now the group's gravel-voiced, tough-as-nails leader, Barney Ross (Sly Stallone) has decided it's time for him to rejoin the band.

For those who keep body counts at these movies, bring lots of paper, with lots of room for hash marks. The count starts early. There's a lull in the film's middle section — for good reason — then it goes off the charts for the finale.

"The Expendables" (2010) introduced audiences to this gaggle of long-in-the-tooth mercenaries, and fueled the film with non-stop action and bloodless violence. It was a huge hit.

"The Expendables 2" (2012) carried on with the same kind of intense violence but added a screwy sense of humor. It was a slightly huger hit.

This sequel to the sequel continues the formula but tosses in a bit of heart, and some back stories that explain who some of these people are and why they do what they do.

For those not familiar with the series, the Expendables are a bunch of guys who will do anything and everything the CIA (secretly, of course) needs them to do. It's a given that will include the use of big guns, big knives, huge explosions, and much mayhem, committed by rough-and-tumble men who are more than slightly over the hill but are talented and fearless and committed — or maybe should be committed.

We learn in this outing that the group started out with five members, at one time reached a high count of 22, and has now been pared down to ... well, to tell the truth, in this one they keep coming and going, so it's hard to keep track.

This third entry also enters into new territory by spinning a tale of revenge. It seems that an early member of the group, Conrad Stonebanks, had a major falling out with Ross, went rogue, did some horrific things, and was, under orders, killed by Ross. Uh-oh, Ross doesn't know it, but he didn't exactly get the job done, and in the midst of an unrelated operation, Ross and the boys stumble upon Stonebanks, now a successful and villainous arms dealer, and Stonebanks stumbles right back upon them, and it's "getting even" time.

The other twist is that Ross is worried about his men getting too old to keep doing this, about mortality, about the fact that Stonebanks is one bad dude. He dismisses everyone, then goes about recruiting a new batch of Expendables — some young blood to pick up the slack and go after Stonebanks with everything they've got, and age on their side.

Everyone is up to the task in the acting department, from the regulars, who have got their characters down pat, to some newcomers, including Kelsey Grammer as Bonaparte, the fellow who helps Ross find the replacements, and all of those new folks, among whom the only familiar face to moviegoers will be Kellan Lutz (from the "Twilight" series). While many eyes will be on the only female member, the rugged and beautiful Luna (a relaxed and natural performance from MMA champ Ronda Rousey), accolades are going flow for Mel Gibson's presentation of Stonebanks. Personally speaking, I don't like the guy or his actions and politics, but he nails this role, and gives the conflicted villain a believable dose of pathos, even as he commits dastardly deeds.

It should be no surprise that the story leads to a big showdown of fisticuffs between the hero and the villain. But it's kind of stunning that the climax is done so well. And it's eye-winkingly apt that the whole thing ends with Neil Young's "Old Man" on the soundtrack.